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Home›Repair guides›External and Internal Low Pressure Fuel Leak Test Procedure

Detroit Diesel — External and Internal Low Pressure Fuel Leak Test Procedure

A Detroit Diesel service procedure — check it applies to your exact model before use.

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Before you start

  • To avoid injury to eye or face, wear a face shield or goggles when conducting a pressure test.
  • The fuel cooler and feed line for the amplifier circuit is located behind the fuel filter module. Ensure this area is not overlooked.

Procedure

  1. Shut off engine and apply the parking brake, chock the wheels, disconnect vehicle battery power, and perform any other applicable safety steps.
  2. Remove the fuel feed and return lines from the fuel filter module.
  3. Install J-48710 fuel pressure test kit onto the module.
  4. Insure the shutoff valve (2) is in the OFF position.
  5. Turn regulator (1) counterclockwise until it stops. The regulator is now set to zero pressure.
  6. Connect to shop air pressure.
  7. Turn the shutoff valve to the ON position.
  8. Turn the regulator clockwise to increase pressure in the fuel system to 75 psi.
  9. Once the system pressure has reached 75 psi, let the system pressure stabilize for one minute then turn the shutoff valve to the OFF position and disconnect shop air from the regulator.
  10. Wait 30 minutes, then check the pressure. The system pressure should not drop over 30 minutes.
  11. Reconnect shop air and turn on the valve.
  12. Use a soapy solution and spray all connectors, fittings, and braided hoses.
  13. Remove oil fill cap and listen for internal air leaks.
  14. Install cooling system pressure testing tool.

Tools required

  • J-48710 fuel pressure test kit
  • shop air pressure
  • face shield or goggles
  • soapy solution spray

Specs & torque values

  • Low pressure fuel system test pressure: 75 psi
  • System pressure stabilization time: 1 minute
  • Pressure drop check time: 30 minutes
  • Maximum allowable pressure drop: 0 psi over 30 minutes

Source: manual:08FSTG11 - EXTERNAL AND INTERNAL LOW PRESSURE FUEL LEAKS.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.